Find the optimal conditions for cryopreservation of human monocytes analysing the following variables: purification methods, concentration of cryoprotectant, controlled cooling rate, the thawing procedure, and dilution and subsequent removal of the cryoprotectant. Once methods for optimal cryopreservation are achieved, functional studies of monocytes from normal donors and from patients with a variety of cancers and under different therapeutic regimens shall be attempted.